The goal of this research is exposure of genetic mechanisms controlling cellular differentiation in Drosophila. Alpha-Amylase was selected as an indicator of the state of differentiation of a tissue so that factors regulating its synthesis, properties, location and ultimate fate may be analyzed during development and in response to environmental changes. The tissue of major interest is the midgut. A system is being developed to selectively screen for mutations of "regulatory genes" which control the structural gene for amylase, Amy, or its products. Genetic analyses utilize variants for electrophoretic mobility, specific activity and heat stability. Amy is tandemly duplicated in D. melanogaster, yet the duplicated loci or their products are independently regulated. Control mechanisms involved will be sought. In D. hydei a single amylase isozyme is present in the midgut of Amy homozygotes; here, starch-diet induced "puffing" activity in the Amy region of polytene chromosomes can be analyzed cytologically. This puffing correlates with enhancement of midgut-specific amylase activity. Amylase, demonstrated by fluorescent antibody techniques, is synthesized in cells showing the puffing. Mutations altering the latter cytological sign of transcription will be selected, if de novo synthesis of amylase can be correlated with the puffing. Amylase synthesis will be quantitated by labelling and specific antibody methods, and its degradation measured. Mutations controlling amylase at the translational level or epigenetically will thus be distinguished. This system will be adapted to melanogaster by increasing the polyteny in midgut cells or by improving resolution of their chromosomes, e.g. by scanning EM. Genetic analysis of the patterns produced by amylase secreting cells in the midgut of melanogaster adults will be pursued. A synthetic compound to selectively screen for amylase deficient mutants will be used in: 1) genetic fine structure analysis of the Amy region; 2) chromosomal location of the Amy gene(s) by overlapping deficiencies; 3) selection of EMS induced regulatory mutants as above; and 4) location of control elements. Molecular characterization of amylase isozymes will continue; sequence divergence will be studied.